The invention relates to a flow-limiting device for a pipe carrying a fluid or gaseous medium which supplies a connected consumer with an essentially constant amount of the medium, which flow-limiting device alters the cross-sectional area of flow through the pipe dependent on the kinetic energy differential upstream and downstream of a spring-loaded body.
The invention is particularly applicable to the controlling and metering of flowing media which are, on the one hand, at an elevated temperature and, on the outer hand, are dirty. Examples are long distance heating mains, but also ammoniacal liquor mains from coal pressure gasification plants which carrying slurries which contain tar and dust.
A known flow-limiting device has a housing which essentially corresponds to a valve housing. It has a seating opposite which a cone-shaped body is displaced in order to alter the cross-sectional area of flow through the pipe. The cone-shaped body sits on a rod to which a membrane is fastened. This is subjected on one side to the pressure upstream of a diaphragm acting as a differential pressure producer and on the other side to the pressure downstream of the diaphragm. The rod is surrounded by a sprial spring. This spring pre-loads the cone-shaped body. This arrangement varies the cross-sectional area of flow through the pipe to permit the passage of a predetermined, substantially constant quantity of the medium.
The complicated construction of such a limiting device is disadvantageous. In particular, control tubes are provided which lead to a chamber containing the membrane, and these control tubes become blocked with dirt from the flowing medium. The limiting device can not be used in these cases.
The task of the invention consists in creating a cheaper and essentially service-free flow-limiting device which is not susceptible to elevated temperatures and dirt in the medium.